Recently a few studies have come out contradicting one another; some say the Moon's interior is wet enough to supply astronauts with water... others say it's pretty dry. The reason water inside the Moon is interesting is because it is linked to how the Moon formed. If it is wet then it will throw our theory of how it formed into question.

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Our Moon formed as the result of a giant impact with Earth, billions of years ago. This was a very high energy and high temperature process, and it is hard to envision how water could have survived it. Now a new study, published today in Science Advances, suggests there is more water on the surface than we thought, which suggests its interior might also be hiding some water.

“Surficial water can be detected basically all over the Moon at all local times of day,” says Christian Wöhler, lead author of the study from TU Dortmund University in Dortmund, Germany.

Previously, water on the Moon’s surface had only been found at its poles.The team used spectroscopy to determine how much water was on the satellite’s surface. This means looking at the light reflected from the surface to search for signs of hydroxyl, a hydrogen atom bonded to an oxygen atom.

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The most accepted theory as to why water exists on the Moon’s surface is that the water molecules formed when protons from the solar wind react with oxygen atoms in the surface of the Moon. If this were the case, we would expect the amount of water on the Moon to vary much more with time. “However, the observed time-of-day-dependent variations are much weaker than expected,” said Wöhler.

This means there must be something else at play, causing the water molecules to be found on the Moon’s surface, and one possibility is that the water is coming from the Moon’s interior.

“Possible sources are, amongst others, hydrated minerals or a reservoir at large depth,” says Wöhler. “This would imply the presence of significant amounts of water in the lunar interior." He adds that the next step will be to map the water on the Moon in much more detail, focussing on specific regions.